1. Field of the Invention
The present invention relates to a process of manufacturing an electronic apparatus, and in particular, to a process control system which controls a manufacturing process, a process control method, and a method of manufacturing an electronic apparatus.
2. Description of the Related Art
In order to realize high-performance electronic apparatuses, a manufacturing process with high accuracy, uniformity, and reproducibility is required. In electronic apparatuses such as semiconductor integrated circuits (ICs) and liquid crystal displays (LCDs), miniaturization and multilayer manufacturing have progressed, and a level of integration has been increased dramatically in order to achieve high-functionality and high-speed performance. For example, in semiconductor apparatuses such as large-scale integrated circuits (LSIs), which are formed of multi-layered micropatterns, it has been made difficult to control the manufacturing process in accordance with the miniaturization thereof. Therefore, an attempt has been made to improve process capability run-to-run (RTR) control by which feedforward (FF) control or feedback (FB) control is carried out between processes or in a process (for example, refer to Jpn. Pat. Appln. KOKAI Publication Nos. 10-275753, 2000-252179 and 2002-151465).
For example, in a trench capacitor manufacturing process, a deep trench is filled up by depositing an amorphous silicon (a-Si) film on the surface of a substrate having a deep trench formed thereon by chemical vapor deposition (CVD) or the like. Thereafter, the a-Si film is etched to a predetermined depth by recess etching such as reactive ion etching (RIE). Usually, the depth of the recess is controlled by controlling an etching time of RIE. In order to control the recess depth precisely, an etching end-point of the a-Si film deposited on the surface of the substrate is detected. An etching rate is calculated on the basis of an end-point detection time from a start of etching to an end-point detection. An etching time for the a-Si film embedded in the deep trench is determined on the basis of a calculated etching rate.
However, an end-point detection time is influenced by not only an etching rate but also a thickness of a deposited a-Si film. Unevenness in a deposited film thickness is brought about among substrates or lots due to variations in CVD conditions for a-Si films. For this reason, even if an etching time for an a-Si film embedded in a deep trench is controlled on the basis of an end-point detection time, a recess depth cannot be controlled with high accuracy. As a result, the process capability for manufacturing a trench-capacitor is reduced, which degrades a manufacturing yield.
Also, conventionally, in manufacture of semiconductor apparatuses, a parameter varying every run with respect to a process having a poor capability, for example, an etching rate or the like, is detected by quality control (QC) measurement after the process is completed. The process capability is improved to thereby increase a yield of semiconductor chips by RTR control using a QC measurement value.
There are cases in which a QC measurement value of a parameter varying every run is made to be an abnormal value different from a tendency of the lot in some of wafers in a lot during processing. Because QC measurement is not carried out on all the wafers in the lot, abnormal values brought about in some of wafers cannot be detected. When such a QC measurement value including an abnormal value is used, FB control or the like does not function effectively. As a result, improvement in control accuracy is made insufficient, which degrades a yield of semiconductor apparatus.